USO0RE41679E

(19) United States (12) Reissued Patent

(10) Patent Number: US (45) Date of Reissued Patent:

Sasaki et a]. (54)

WIDE VIEWING ANGLE POLARIZER AND LIQUID-CRYSTAL DISPLAY DEVICE

6,476,892 B2 * 11/2002

6,531,195 B2 6,606,140 B1 *

(75) Inventors: Shinichi Sasaki, Ibaraki (JP); Takashi Yamaoka, Ibaraki (JP); Nao Murakami, Ibaraki (JP); Hiroyuki Yoshimi, Ibaraki

(JP) (73) Assignee: Nitto Denko Corporation, Osaka (JP)

(21) Appl.No.: 10/974,958 (22) Filed:

Oct. 28, 2004

Patent No.:

Appl. No.:

6,717,642 Apr. 6, 2004 10/266,943

Filed:

Oct. 9, 2002

Issued:

(30) (51)

(JP)

Aminaka .................. .. 349/117

3/2003 Negoro et a1. 8/2003

Ito et a1. ................... .. 349/123

5/2003 Sasakietal. 6/2003 Sasakietal.

FOREIGN PATENT DOCUMENTS JP JP JP JP JP JP

03-009325 03-067219 03-140921 05-061039 06-186534 09-133810

KR

10-0629045

* * * * * *

1/1991 3/1991 6/1991 3/1993 7/1994 5/1997

4/2003

Primary ExamineriRichard H Kim

(74) Attorney, Agent, or Firmisughrue Mion, PLLC (57) ABSTRACT

A Wide vieWing angle polariZer having: a polarizing ?lm;

Foreign Application Priority Data

Oct. 10, 2001

Sep. 14, 2010

* cited by examiner

Related US. Patent Documents

Reissue of:

(64)

2003/0086033 A1 2003/0103186 A1

RE41,679 E

................................... ..

P2001-312162

and a phase retarder adhesively laminated on at least one

surface of the polarizing ?lm through an adhesive layer, the phase retarder being made of a composite phase retarder constituted by a laminate in Which a retardation layer B of a

Int. Cl.

cholesteric liquid crystal-oriented solidi?ed layer in a selec

(2006.01)

G02F 1/1335

tive re?ection Wavelength range of not larger than 350 nm is supported by a retardation layer A of a thermoplastic resin

(52)

US. Cl. ...................................... .. 349/118; 349/119

(58)

Field of Classi?cation Search ...................... .. None

exhibiting positive birefringence, the composite phase

See application ?le for complete search history.

retarder being formed so that the laminate has Re of not

References Cited

smaller than 10 nm and Rth-Re of not smaller than 50 nm When Re and Rth are de?ned as Re=(nx—ny)X d and Rth=

U.S. PATENT DOCUMENTS

main refractive indices, n2 is a thicknessWise refractive

(56)

(nx—nZ)X d respectively in Which nx and ny are in-plane 5,241,408 A 5,543,948 A 5,737,047 A

8/1993 Ishikawa et a1. 8/1996 Takahashiet a1. *

4/1998

Sakamoto et a1. ......... .. 349/119

6,025,958 A

2/2000 Yamaoka et a1.

6,380,996 B1 *

4/2002 Yokoyama et a1. ........ .. 349/117

6,407,787 B1

6/2002 Sekime et a1.

index, and d is a layer thickness. A liquid-crystal display device having: a liquid-crystal cell; and a Wide vieWing angle polariZer de?ned above and disposed on at least one surface of the liquid-crystal cell. 4 Claims, 1 Drawing Sheet

12

\\\\\\\\~ 1 ///////j ~ 1*

V/////////////*~Y

V/////////M

1‘

US. Patent

Sep.14,2010

US RE41,679 E

FIG. 1

FIG. 2

\\\\\\Y 7//////A 7/////////A V////////////%

\\\\\\\\ ///////

FIG. 3

FIG. 4

\\\\\\\ / //////

\\\\\\\\ ///////j

V//////////<

V//////////////

\.

>/////////

\\ \\\\\ %///////////// /

V////////////%

V/////////A

\\\\\\\\\\\\

'

US RE41,679 E 1

2

WIDE VIEWING ANGLE POLARIZER AND

uid crystal-oriented solidi?ed layer in a selective re?ection wavelength range of not larger than 350 nm is supported by a

LIQUID-CRYSTAL DISPLAY DEVICE

retardation layer A of a thermoplastic resin exhibiting posi

tive birefringence, the composite phase retarder being

Matter enclosed in heavy brackets [ ] appears in the original patent but forms no part of this reissue speci?ca

formed so that the laminate has Re of not smaller than 10 nm and Rth-Re of not smaller than 50 nm on the basis of light at a wavelength of 590 nm when Re and Rth are de?ned as

tion; matter printed in italics indicates the additions made by reissue. The present application is based on Japanese Patent

Re=(nx—ny)X d and Rth=(nx—nz)X d respectively in which

Application No. 2001 -312162, which is incorporated herein

nx and ny are in-plane main refractive indices, nz is a thick

by reference.

nesswise refractive index, and d is a layer thickness. There is also provided a liquid-crystal display device having: a

liquid-crystal cell; and a wide viewing angle polarizer

BACKGROUND OF THE INVENTION

de?ned above and disposed on at least one surface of the

1. Field of the Invention The present invention relates to a wide viewing angle

liquid-crystal cell. According to the invention, the retardation layer B is

polarizer adapted for improvement in viewing angle charac

excellent in reduction in thickness because it is made of a

teristic of a liquid-crystal display device such as a vertical

liquid-crystal coating ?lm. Moreover, because the retarda tion layer B is supported by the retardation layer A, a high quality composite phase retarder excellent in reduction in

aligned (VA) liquid-crystal display device. 2. Description of the Related Art To form a liquid-crystal display device exhibiting excel

20

thickness can be obtained. Moreover, because the composite

lent display quality in all azimuths by compensation for bire fringence of a liquid-crystal cell achieving display through a

phase retarder is bonded to a polarizing ?lm so as to serve as

polarizer, the polarizer needs to be combined with a phase

tive layer to be bonded to the polarizing ?lm can be omitted. Hence, greater reduction in thickness can be achieved. When

a transparent protective layer, a separate transparent protec

retarder in which main refractive indices nx, ny and nz in

three directions, that is, two in-plane directions x and y in association an obliquely viewing direction and one normal

25

polarizing ?lm is used, the viewing angle of the liquid crystal cell can be improved extremely.

direction z, are controlled. Particularly in a VA or OCB

liquid-crystal display device, the polarizer needs to be com bined with a phase retarder in which the main refractive indices in the three directions satisfy the relation nx>ny>nz. As the phase retarder with controlled nx, ny and nz used in combination with the polarizer, there is heretofore known a

the combination of the composite phase retarder and the

Features and advantages of the invention will be evident 30

from the following detailed description of the preferred embodiments described in conjunction with the attached

drawings.

phase retarder made from uniaxially stretched ?lms lami nated so that in-plane slow axis directions are perpendicular to each other or a monolayer phase retarder formed from a

BRIEF DESCRIPTION OF THE DRAWING 35

ment; 40

object.

In the accompanying drawings: FIG. 1 is a sectional view for explaining an embodiment; FIG. 2 is a sectional view for explaining another embodi

high-molecular ?lm laterally or biaxially stretched by a ten ter. Each of these phase retarders is bonded to a polarizer having a transparent protective layer such as a triacetyl cel lulose ?lm through an adhesive layer to thereby form an

FIG. 3 is a sectional view for explaining a further embodi

ment; and

Use of the former phase retarder, however, brings about a problem that the volume of the phase retarder is large

FIG. 4 is a sectional view for explaining a still further embodiment.

because of use of two retardation ?lms. On the other hand, the range of retardation value obtained in the latter mono layer phase retarder is narrow. In the case where the latter

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

monolayer phase retarder is used and retardation value in the direction of the thickness of the phase retarder is remarkably

The wide viewing angle polarizer according to the inven tion has: a polarizing ?lm; and a phase retarder adhesively

larger than that in the normal direction, two or more phase retarders need to be laminated in the same manner as the

former phase retarder in order to obtain the required retarda tion value. There arises still the problem that the volume of

laminated on at least one surface of the polarizing ?lm 50

the phase retarder is large.

teric liquid crystal-oriented solidi?ed layer in a selective re?ection wavelength range of not larger than 350 nm is

SUMMARY OF THE INVENTION 55

An object of the invention is to provide a phase retarder containing polarizer which is excellent in reduction in thick play device such as a VA liquid-crystal display device 60

trast.

ing angle polarizer having: a polarizing ?lm; and a phase retarder adhesively laminated on at least one surface of the

laminate in which a retardation layer B of a cholesteric liq

Re of not smaller than 10 nm and Rth-Re of not smaller than 50 nm on the basis of light at a wavelength of 590 nm when Re and Rth are de?ned as Re=(nx—ny)X d and Rth=(nx

nz)X d respectively in which nx and ny are in-plane main refractive indices, nz is a thicknesswise refractive index, and d is a layer thickness. Hereupon, nx is an in-plane refractive

According to the invention, there is provided a wide view

polarizing ?lm through an adhesive layer, the phase retarder being made of a composite phase retarder constituted by a

supported by a retardation layer A (?rst retardation layer) of a thermoplastic resin exhibiting positive birefringence. The composite phase retarder is formed so that the laminate has

ness and which can be used for forming a liquid-crystal dis

improved in viewing angle characteristic and high in con

through an adhesive layer. The phase retarder is made of a composite phase retarder constituted by a laminate in which a retardation layer B (second retardation layer) of a choles

65

index in the direction in which the in-plane refractive index becomes maximum within the plane of the plate, and ny is an in-plane refractive index in the direction orthogonal to the direction of nx.

US RE41,679 E 4

3 Examples of the Wide vieWing angle polariZer 11 are

a visible region but transmitting the light. That is, the choles

shown in FIGS. 1 to 4. In FIGS. 1 to 4, the reference numeral

teric liquid crystal exhibits characteristic of selectively

3 designates a polarizing ?lm; 4, an adhesive layer; 5, a retardation layer A; and 7, a retardation layer B. Incidentally, the reference numeral 1 designates a transparent protective layer; 2 and 6, adhesive layers; and 8, an oriented ?lm.

re?ecting part of light at Wavelengths near the central Wave length of incident light at a Wavelength nc-P parallel to a

spiral axis, as one of left- and right-hand circularly polariZed light components When nc is the average refractive index and P is the spiral pitch on the basis of the spiral oriented state of

The retardation layer A, Which is one of constituent mem

the cholesteric liquid crystal. If the selective re?ected light region appears in the visible region, the quantity of light alloWed to be used for display is reduced disadvantageously. Therefore, the cholesteric liquid crystal is provided for pre venting the quantity of light from being reduced.

bers of the composite phase retarder 10, is made of a thermo

plastic resin exhibiting positive birefringence. That is, the retardation layerA is made of a thermoplastic resin exhibit ing characteristic of na>nb in Which na is a refractive index in a stretching direction and nb is a refractive index in an

in-plane direction perpendicular to the stretching direction

As the cholesteric liquid crystal, there can be used a suit able one exhibiting the aforementioned selective re?ecting

When a ?lm of the resin is stretched uniaxially.

The thermoplastic resin is not particularly limited. Any

characteristic as described in Unexamined Japanese Patent

suitable transparent resin exhibiting positive birefringence

Publications No. Hei. 3-67219, 3-140921, 5-61039,

can be used as the thermoplastic resin. Examples of the ther

6-186534 and 9-133810, etc. From the point ofvieW of sta bility of the oriented solidi?ed layer, there can be preferably used a liquid-crystal material capable of forming a choles teric liquid-crystal layer, such as a cholesteric liquid-crystal polymer, a chiral agent-containing nematic liquid-crystal polymer or a compound capable of forming the aforemen

moplastic resin include polycarbonate, polyallylate,

polysulfone, polyole?n, polyethylene terephthalate, polyeth ylene naphthalate, norbomene-based polymer, cellulose

20

based polymer, and mixture polymer of tWo or three or more

kinds of polymers selected from the aforementioned poly mers. Particularly, a resin excellent in birefringence

tioned liquid-crystal polymer by polymeriZation With light,

controllability, transparency and heat resistance is used pref

heat or the like.

erably.

25

For example, the retardation layer B can be formed in

The retardation layer A can be formed in such a manner

such a manner that a support base material is coated With

that a ?lm of the thermoplastic resin produced by a suitable

cholesteric liquid crystal. In this case, a method of Wet-on Wet coating the support base material With one kind or differ ent kinds of cholesteric liquid crystal may be used in accor dance With necessity in order to control retardation. As the coating method, there can be used a suitable method such as a gravure coating method, a die coating method or a dipping

method such as an extrusion molding method or a cast ?lm

forming method is stretched by a method such as a vertical stretching method using a roll or a lateral or biaxial stretch

ing method using a tenter. The stretching temperature is preferably selected to be near the glass transition tempera ture (Tg) of the ?lm as a subject of treatment. Particularly, the stretching temperature is preferably selected to be not loWer than Tg and loWer than the melting point of the ?lm. In the vertical stretching method using a roll, there can be

30

method. The retardation layer A or any other suitable poly mer ?lm may be used as the support base material. 35

not particularly limited. Any suitable method that can orient a liquid-crystal compound can be used. Incidentally, an

used a suitable heating method such as a method using a

heating roll, a method of heating an atmosphere or a method

using the aforementioned methods in combination. In the

40

biaxial stretching method using a tenter, there can be used a suitable method such as a simultaneous biaxial stretching method using a Whole tenter technique or a sequential

biaxial stretching method using a roll-tenter technique. A layer little in variation in orientation and retardation is pref erably used as the retardation layer A. The thickness of the retardation layer A can be decided suitably in accordance With retardation or the like. Generally, from the point of vieW of reduction in thickness, the thickness of the retardation layer A is selected to be in a range of from 1 to 300 um, particularly in a range of from 10 to 200 pm, more particu larly in a range of from 20 to 150 pm.

For the formation of the retardation layer B, a method for

orienting liquid crystal may be used. The orienting method is

45

example of the method is a method of orienting liquid crystal With Which an oriented ?lm is coated. Examples of the ori ented ?lm include: a rubbing-treated ?lm of an organic com pound such as a polymer; a rhombic vapor-deposited ?lm of an inorganic compound; a ?lm having a micro-groove; and a ?lm obtained by accumulation of an LB ?lm formed from an

organic compound such as dioctadecyl methyl ammonium chloride or methyl stearate by the Langmuir-Blodgett tech

nique. Further, an oriented ?lm capable of generating an orient 50

ing function When irradiated With light maybe used. On the other hand, a method of orienting liquid crystal With Which a stretched ?lm is coated (Unexamined Japanese Patent Publi cation No. Hei. 3-9325) or a method of orienting liquid crys tal under application of an electric ?eld, a magnetic ?eld or

On the other hand, the retardation layer B, Which is one of

constituent members of the composite phase retarder, is

formed as a solidi?ed layer obtained in such a manner that 55 the like may be used. Incidentally, it is preferable that the

oriented state of liquid crystal is as uniform as possible. It is also preferable that liquid crystal is provided as a solidi?ed layer in Which the oriented state is ?xed.

cholesteric liquid crystal in a selective re?ection Wavelength range of not larger than 350 nm is oriented and then the oriented state is ?xed. The thickness of the retardation layer B can be also decided suitably in accordance With retarda tion or the like. Generally, from the point of vieW of reduc

The composite phase retarder is formed in such a manner 60

that the retardation layer B is supported by the retardation

tion in thickness, the thickness of the retardation layer B is

layer A in order to achieve reduction in thickness. For

selected to be not larger than 20 um, particularly in a range of from 0.1 to 15 pm, more particularly in a range of from

example, as shoWn in FIGS. 1 and 2, the composite phase retarder is formed by a method in Which a coating liquid

0.5 to 10 pm.

The cholesteric liquid crystal in a selective re?ection Wavelength range of not larger than 350 nm is used for

achieving bright display by not selectively re?ecting light in

65

layer or a coating ?lm provided on a support base material to form the retardation layer B 7 is transferred and bonded onto the retardation layer A 5 through an adhesive layer 6 as occasion demands. For example, the transfer can be per

US RE41,679 E 5

6

formed by a method including the steps of: forming the

layer is not particularly limited in kind. From the point of vieW of preventing the optical characteristic of constituent

retardation layer B on a releasant-treated surface provided on the support base material; providing an adhesive layer on

members from changing, it is preferable to use an adhesive

agent not requiring any high-temperature process for curing

the retardation layer B as occasion demands; laminating the retardation layerA on the retardation layer B; and separating the support base material through the releasant-treated sur face.

and drying in a bonding treatment or an adhesive agent not

requiring any long-term curing and drying process. From this point of vieW, a hydrophilic polymer-based adhesive agent or a pressure sensitive adhesive layer may be prefer

On the other hand, as shoWn in FIGS. 3 and 4, the com

ably used.

posite phase retarder in Which the retardation layer B is sup ported by the retardation layer A can be also formed by a method including the steps of: providing the oriented ?lm

Incidentally, for the formation of the pressure sensitive adhesive layer, it is possible to use a transparent pressure sensitive adhesive agent using a suitable polymer such as

such as a rubbing ?lm 8 on a surface of the retardation layer A 5 serving as one of constituent members of the composite

acrylic-based polymer, silicone-based polymer, polyester, polyurethane, polyether or synthetic rubber. Particularly, an acrylic-based pressure sensitive adhesive agent is preferred from the point of vieW of optical transparency, pressure sen

phase retarder, as occasion demands; and orienting and ?x ing a cholesteric liquid-crystal layer on the oriented ?lm.

This method is particularly preferred from the point of vieW of reduction in thickness. The composite phase retarder is formed as a laminate exhibiting retardation characteristic in Which Re is not smaller than 10 nm, particularly in a range of from 20 to

sitive adhesion, Weather resistance, and so on.

Incidentally, the pressure sensitive adhesive layer may be provided on one or each of opposite surfaces of the Wide 20

1000 nm, more particularly in a range of from 25 to 500 nm

and Rth-Re is not smaller than 50 nm, particularly in a range of from 70 to 1500 nm, more particularly in a range of from 100 to 800 nm, on the basis of light at a Wavelength of 590

nm (this condition applies hereunder) When Re and Rth are de?ned as Re=(nx—ny)X d and Rth=(nx—nz)X d in Which nx and ny are in-plane main refractive indices (in directions of sloW and fast axes), nz is a thicknessWise refractive index, and d is a layer thickness.

The provision of the composite phase retarder exhibiting

vieWing angle polarizer as occasion demands in order to bond the Wide vieWing angle polarizer to a subject such as a liquid-crystal cell. In this cases if the pressure sensitive

adhesive layer is exposed, the pressure sensitive adhesive layer is preferably temporarily covered With a separator or 25

30

the like so that a surface of the pressure sensitive adhesive

layer can be prevented from being contaminated With an alien substance before the pressure sensitive adhesive layer is put into practical use. The Wide vieWing angle polarizer may be formed to have at least one suitable functional layer on one or each of its

opposite surfaces. Examples of the functional layer include: a protective layer similar to the transparent protective layer

the retardation characteristic can compensate for birefrin gence of any kind of liquid-crystal cell such as a VA liquid crystal cell or an OCB liquid-crystal cell and can be used for

retarder exhibiting the retardation characteristic can be

for various kinds of purposes such as Water resistance; and an anti-re?ection layer or/ and an anti-glare layer for the pur pose of preventing surface re?ection or the like. The anti re?ection layer can be formed suitably as a light-coherent

obtained by a method using the retardation layer A having

?lm such as a ?uorine-based polymer coat layer or a multi

Re of 20 to 300 nm and Rh/Re of 1.0 to 50 and the retarda tion layer B having Re of 0 to 20 nm and Rth of 30 to

formed as a resin coating layer containing ?ne particles or by

forming a liquid-crystal display device excellent in vieWing angle and contrast. For example, the composite phase

35

layer metal-deposited ?lm. The anti-glare layer can be also 40

500 nm.

The Wide vieWing angle polarizer can be formed in such a manner that the composite phase retarder is adhesively lami nated on one or each of opposite surfaces of the polarizing ?lm 3 as shoWn in FIGS. 1 to 4. As the polarizing ?lm, it is possible to use a suitable one in accordance With the related

a suitable method in Which a ?ne prismatic structure is pro vided on a surface by a suitable method such as embossing,

sandblasting or etching to thereby diffuse surface-re?ected

light. 45

Incidentally, examples of the ?ne particles include inor ganic ?ne particles and organic ?ne particles With a mean particle size of from 0.5 to 20 um. The inorganic ?ne par ticles are made of silica, calcium oxide, alumina, titania,

art Without any particular limitation. For example, it is pos sible to use a polarizing ?lm produced by the steps of: adsorbing a dichroic substance constituted by iodine and/or

zirconia, tin oxide, indium oxide, cadmium oxide, antimony

a dichroic dye such as an azo dye, an anthraquinone dye or a 50 oxide, etc. and may be electrically conductive. The organic ?ne particles are crosslinked or non-crosslinked ?ne par tetrazine dye onto a ?lm made of a hydrophilic polymer such

as polyvinyl alcohol, partially formalized polyvinyl alcohol or partially saponi?ed ethylene-vinyl acetate copolymer; and stretching and orienting the ?lm. When the composite phase retarder is provided on only one surface of the polariz ing ?lm 3 as shoWn in FIGS. 1 to 4, a transparent protective layer made of a transparent ?lm or the like may be provided on the other surface of the polarizing ?lm 3 as occasion demands. A ?lm excellent in isotropy such as a triacetyl cellulose ?lm can be preferably used as the transparent pro

ticles made of suitable polymers such as polymethyl meth acrylate and polyurethane. One member or a combination of tWo or more members suitably selected from the inorganic 55

sensitive adhesive layer may contain such ?ne particles so as to exhibit light-diffusing characteristic.

The Wide vieWing angle polarizer according to the inven 60

tective layer.

tion can be used for suitable purposes such as formation of a

liquid-crystal display device 12. Particularly, the Wide vieW ing angle polarizer can be preferably used for optical com pensation of a liquid-crystal cell 9. The liquid-crystal display

The retardation layer adjacent to the polarizing ?lm may be A or B as shoWn in FIGS. 1 to 4. The adhesive layer for

bonding the composite phase retarder and the polarizing ?lm to each other is provided to prevent the optical axis from being displaced and prevent an alien substance such as dust from entering. The adhesive agent for forming the adhesive

?ne particles and the organic ?ne particles may be used as the ?ne particles. Incidentally, the adhesive layer or pressure

device can be formed by arrangement of the Wide vieWing 65

angle polarizer on one or each of opposite surfaces of the

liquid-crystal cell. In this case, either of the composite phase retarder and the polarizing ?lm may be disposed on the

US RE41,679 E 7

8

liquid-crystal cell side. Incidentally, for the formation of the

EXAMPLE 4

liquid-crystal display device, suitable optical elements such

A Wide vieWing angle polariZer Was obtained in the same manner as in Example 3 except that the composite phase retarder With the retardation layers A and B inverted to each other in location Was disposed so that the retardation layer B faced inWard.

as a light-diffusing plate, a backlight unit, a light-condensing sheet or a re?ecting plate may be disposed as occasion demands. EXAMPLE 1

EXAMPLE 5 A triacetyl cellulose ?lm Was laterally stretched by a ten ter to thereby obtain a retardation layer A having Re of 38

A polyester ?lm (PET) Was vertically stretched through a heating roll to thereby obtain a retardation layer A having Re of 40 nm, Rth of41 nm and a thickness of 60 um.

nm, Rth of 65 nm and a thickness of 49 um. A solution

containing 1% by Weight of polyvinyl alcohol Was applied on the retardation layerA and dried at 90° C. to thereby form a coating ?lm about 0.01 pm thick. A surface of the coating ?lm Was rubbing-treated to form an oriented ?lm. Then, a

cholesteric liquid-crystal solution the same as in Example 1 Was applied on the oriented ?lm, heated at 90° C. for 1 minute and crosslinked by irradiation With ultraviolet rays to form a retardation layer B having a thickness of 1.5 pm, Re

On the other hand, a nematic liquid-crystal compound represented by the aforementioned formula and a chiral agent represented by the folloWing formula Were mixed With each other to set a selective re?ection Wavelength to be in a range of from 290 to 310 nm. A cholesteric liquid-crystal

20

of 2 nm and Rth of 106 nm. In this manner, a composite phase retarder having Re of 40 nm and Rth of 171 nm Was

solution obtained by adding a photo-polymeriZation initiator

obtained. A Wide vieWing angle polariZer having a total

to the mixture Was applied on a biaxially stretched PET ?lm, heated at 80° C. for 3 minutes and then crosslinked by irra diation With ultraviolet rays to thereby obtain a retardation layer B having a thickness of 1.9 um, Re of 2 nm and Rth of

thickness of 166 um Was obtained in the same manner as in

Example 1 except that the composite phase retarder obtained 25

thus Was used. Incidentally, the triacetyl cellulose ?lm Was

bonded through a polyvinyl alcohol adhesive layer 5 pm

132 nm. The retardation layer B Was laminated on the retar

thick.

dation layer A through an acrylic-based pressure sensitive adhesive layer having a thickness of 15 pm. The biaxially

EXAMPLE 6

A Wide vieWing angle polariZer Was obtained in the same manner as in Example 5 except that the composite phase

stretched PET ?lm Was separated to thereby obtain a com

posite phase retarder having Re of 42 nm and Rth of 173 nm.

H

CH3

Then, a polyvinyl alcohol ?lm 80 pm thick Was stretched by ?ve times in an iodine aqueous solution to thereby obtain a polariZing ?lm. A triacetyl cellulose ?lm 80 um thick Was bonded to one surface of the polariZing ?lm through an

acrylic-based pressure sensitive adhesive layer. The compos ite phase retarder Was bonded to the other surface of the polarizing ?lm through a pressure sensitive adhesive layer so that the retardation layerA faced inWard. Thus, a Wide vieW ing angle polariZer having a total thickness of 210 um Was obtained.

retarder With the retardation layers A and B inverted to each other in location Was disposed so that the retardation layer B faced inWard. 45

Comparative Example A polariZer obtained by bonding triacetyl cellulose ?lms 50

EXAMPLE 2

A Wide vieWing angle polariZer Was obtained in the same manner as in Example 1 except that the composite phase retarder With the retardation layers A and B inverted to each other in location Was disposed so that the retardation layer B faced inWard.

Evaluation Test 55

(Wide vieWing angle) polariZers obtained in each of Examples and Comparative Example Were disposed on

EXAMPLE 3

A composite phase retarder having Re of 41 nm and Rth of 173 nm and a Wide vieWing angle polariZer having a total

onto opposite surfaces of a polariZing ?lm obtained in Example 1 Was used singly.

60

opposite surfaces of a VA liquid-crystal cell in the form of crossed-Nicol to thereby obtain a liquid-crystal display device. A vieWing angle exhibiting contrast of not loWer than

thickness of 231 um Were obtained in the same manner as in

10 Was measured in each of an up-and-doWn direction, a

Example 1 except that the retardation layer A Was made of a norbornene resin ?lm laterally stretched by a tenter and hav ing Re of 40 nm, Rth of 102 nm and a thickness of 85 um

left-and-right direction, a direction of diagonal 1 (45° and —225°) and a direction of diagonal 2 (135° and 315°). Incidentally, the composite phase retarder Was disposed on the cell side in Examples 1 and 2 Whereas the polariZing ?lm

Whereas the retardation layer B Was formed to have a thick ness of1.0 um, Re of1nm and Rth of71nm.

65

Was disposed on the cell side in the other Examples.

US RE41,679 E 9

10 retarder constituted by a ?rst retardation layer and a second retardation layer, which is a laminate in which

Results of the measurement were as shown in Table.

[a] the second retardation layer of a cholesteric liquid crystal-oriented solidi?ed layer in a selective re?ection wavelength range of not larger than 350 nm is sup

Viewing Angle

Up-Down

Left-Right

Diagonal l

Diagonal 2

X80 X80 X80 X80 X80 X80 X40

X80 X80 X80 X80 X80 X80 X40

X65 X65 X60 X60 X65 X65 X30

X65 X65 X60 X60 X65 X65 X30

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative

ported by [a] the ?rst retardation layer of a thermoplas tic resin exhibiting positive birefringence, said compos ite phase retarder being formed so that said laminate has Re of not smaller than 10 nm and Rth-Re of not smaller than 50 nm on the basis of light at a wavelength of 590 nm when Re and Rth are de?ned as Re=(nx—

ny)X d and Rth=(nx—nZ)X d respectively in which nx

Example

and ny are in-plane main refractive indices, n2 is a

thicknesswise refractive index, and d is a layer thick

It is obvious from Table that the viewing angle exhibiting high contrast is widened in Examples. It is obvious from the

ness.

2. A wide viewing angle polariZer according to claim 1, wherein said ?rst retardation layer in said composite phase

above description that a wide viewing angle polariZer which can be used for forming a liquid-crystal display device thin

in thickness, light in weight, excellent in productivity and visibility and high in display quantity is obtained according

retarder has Re of 20 to 300 nm and Rth/Re of not smaller 20

to the invention.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form can be changed in the details of construction and in the combination

to 500 nm.

3. A wide viewing angle polariZer according to claim 1, wherein a pressure sensitive adhesive layer is provided on at 25

4. A liquid-crystal display device comprising:

and the scope of the invention as hereinafter claimed. What is claimed is:

1. A wide viewing angle polariZer comprising: a phase retarder adhesively laminated on at least one sur

face of said polarizing ?lm through an adhesive layer, said phase retarder being made of a composite phase

least one of opposite surfaces of said wide viewing angle

polariZer.

and arrangement of parts without departing from the spirit

a polarizing ?lm; and

than 1.0 whereas said second retardation layer in said com posite phase retarder has Re of 0 to 20 nm and Rth[/Re] of 30

30

a liquid-crystal cell; and a wide viewing angle polariZer according to claim 1 and disposed on at least one surface of said liquid-crystal

cell.